1. Field of the Invention
The present invention relates to insecticides, to methods of making insecticides, and to a method of using insecticides. In another aspect, the present invention relates to insecticides having enhanced UV stability, to methods of making insecticides more UV stable, and to a method of using such insecticides. In even another aspect, the present invention relates to microbial insecticides having enhanced UV stability, to methods of making such insecticides, and to a method of using such insecticides. In still another aspect, the present invention relates to microbial insecticides having enhanced UV stability by utilizing a common dietary constituent that is directly bonded to the microbial pathogen, to methods of making such insecticides, and to a method of using such insecticides.
2. Description of the Related Art
Insects can be infected by viruses, bacteria, protozoa, fungi, rickettsiae and nematodes. Some of these disease organisms may be very pathogenic to their hosts and cause a high rate of mortality. During the last several decades it has been successfully demonstrated that insect pathogens can be applied for the temporary control of insect pests. A growing number of commercial products using Bacillus thuringiensis (BT) strains, nuclear polyhedrosis viruses (NPV), granulosis viruses, microsporidians, nematodes, and fungi have been developed. The high specificity and low environmental impact of these pathogens have made them particularly attractive components for insect pest management. With the advent of genetic engineering, it has become routine to express novel insecticidal proteins in some of these pathogens, particularly the baculoviruses. The toxins from BT have also been expressed directly in crop plants, but molecular techniques are also being utilized to enhance the toxicity and host range of various BT isolates to use as spray treatments. These developments assure that the market will see an increasing number of genetically modified microbial pesticides that offer safer alternative to synthetic pesticides.
However, several environmental factors may limit the persistence and efficacy of these agents. The foremost destructive factor limiting their performance in the field is sunlight. Ultraviolet radiation is known to rapidly inactivate viruses, bacteria, mirosporidians, and fungi within hours to days. Consequently, considerable research effort has taken place to increase the persistence of the pathogens for as long as possible.
The most commonly attempted method to enhance UV-stability in the field for BT and NPV has been to use spray formulations containing sunlight screens. A host of materials have been tested for improving sunlight persistence. These compounds can be classified as those that reflect UV and those that absorb UV light. The following tables list some of the compounds that have been tested and in some cases, obtained patents for UV protection of NPV and/or BT:
TABLE 1 ______________________________________ UV Reflectants Used for Protecting Microbial Pesticides Concen- trations Protectant Protectant used Source ______________________________________ aluminum oxide AlO.sub.2 50:1 Al:NPV aluminum powder Al Blancophor SV .RTM. TiO.sub.2 Chemical Developments of Canada Tinopal CBS .RTM. stilbene Ciba Geigy, Co. derivative Tinopal RBS200 .RTM. stilbene Ciba Geigy, Co. derivative ______________________________________
TABLE 2 ______________________________________ UV Absorbants Concen- trations Protectant Composition used Source ______________________________________ Amelozan .RTM.) 0.05% Hoechst Chemical Co. FDR benzyl cinnamate 3% carbon india ink, 1 kg/ha Activated Carbon activated carbon, Co. Pittsburg, PA etc. 15230 Chevron .RTM. 2.0% Chevron Chemical Co. USA. lignin sulphate natural phenolic 8.5% polymer soy hydrosylate 3% yeast 5% milk 3% Egg albumin 3% Nutritional Biochemicals Corp. USA NuFilm 17 .RTM. SAN-240 wp(75) .RTM. Sandoz Inc. Homestead, Fl Shade IMC 90001 .RTM. flavonoids 0.25 to Sandoz Inc. (probably 6.0% Homestead, Fl quercetin) Unival DS49 .RTM. 1.0% ______________________________________
Several factors limit the use of these protectants. First high application rates of most of the compounds are not cost effective. Tank mixes requiring up to 8% of any of the additives becomes cost prohibitive. Also, high usage rates of reflectant compounds may severely disrupt photosynthesis on leaf surfaces. Some compounds such as the aluminum derivatives and stilbenes may be relatively toxic and thus should not be used. Shade.RTM. (presumably a flavonoid plant product) was one of the most widely tested compounds but produced sporadic results and required high concentrations (up to 6%) for effective protection.
Thus there is a need in the art for insecticides, and methods of making insecticides which do not suffer from the disadvantages of the prior art.
There is another need in the art for insecticides with enhanced UV stability.
There is even another need in the art for insecticides with reduced toxicity.
There is still another need in the art for insecticides with reduces application rates.